1. Field of the Invention
The present invention relates to a novel L-fucose dehydrogenase (hereafter referred to as L-FDH) which acts on L-fucose to produce L-fuconolactone and at the same time, converts oxidized nicotinamide adenine dinucleotide phosphate (NADP.sup.+) into reduced nicotinamide adenine dinucleotide (NADPH), a process for production thereof, a method for enzymatically assaying L-fucose using L-FDH and a kit for the quantitative assay.
2. Description of the Prior Art
It was pointed out that complex carbohydrates or glycoconjugates bound to proteins or lipids took a part in information transfer of the living body. Since then, findings on these sugars are rapidly increasing. In these findings, there is a report that L-fucose increases or decreases depending upon pathological conditions of lung cancer [Clin. Chem., vol. 22, No. 9, 1516-1521 (1976)]. It is thus expected that determination of this sugar would give useful information on pathological conditions of the patient with lung cancer.
In order to determine L-fucose, a method using an enzyme is excellent in accuracy and simplicity. As enzymes for quantitative determination of L-fucose, there are known L-FDH of pork liver origin [J. Biol. Chem., Vol. 244, 4785-4792 (1969)], L-FDH of sheep liver origin [Arch. Biochem. Biophys., Vol. 186, 184-188 (1978)], L-FDH of rabbit liver origin [J. Biochem., Vol. 86, 1559-1565 (1979)], L-FDH derived from bacteria belonging to the genus Corynebacterium (Japanese Patent Application Kokai (Laid-Open) No. 62-155085), L-FDH derived from Pullularia pullulans [Arq. Biol. Tecnol., Vol. 30, 361-366 (1987)] and the like. These enzymes are all dehydrogenasses utilizing nicotinamide adenine dinucleotide (NAD.sup.+) as coenzyme.
Several attempts to quantitatively determine L-fucose using these enzymes have also been proposed in, for example, Japanese Patent Application Kokai (Laid-Open) No. 62-175197, Anal. Biochem., Vol. 121, 129-134 (1982), Anal. Biochem., Vol. 112, 76-81 (1981), Methods Enzym. Anal. (3rd Ed.), Vol. 6, 387-398, etc.
Where a part of the living body, for example, serum or the like is used as a sample and its component is enzymatically assayed, as a matter of course, it is desired to design the assay system in such a fashion that enzymes or metabolites in the metabolic systems naturally contained in the living body are minimized as less as possible.
From this viewpoint, the use of dehydrogenase utilizing NADP.sup.+ as coenzyme for assay is superior to the use of dehydrogenase utilizing NAD.sup.+ as coenzyme. This is because that enzymes (e.g., lactate dehydrogenase, etc.) utilizing NAD (or NADH) are contained in serum and the like in relatively large quantities and their metabolites (e.g., pyruvate, lactate, etc.) are always contained therein and hence, the NAD.sup.+ quantitative assay system tends to be readily affected by these compounds.